Take the Continental-operated ExpressJet Flight 2816. On Aug. 7, 2009, bad weather diverted the Houston-to-Minneapolis flight to Rochester, Minn., where the tiny commuter plane sat packed with 47 passengers from midnight to 6:30 a.m. No one was allowed off, and passengers were offered only one drink. When the door was finally opened, they ran to the counter to complain.

While this was an extreme example of flights gone bad, we’ve all had problems while flying. The airline lost my bag! That gate agent was so rude! I missed my connection!

Sometimes we can brush it off as an unfortunate consequence of air-travel convenience. But other times we just can’t let it go. Fortunately, plenty of outlets exist for expressing our frustrations and rectifying problems.

The airline itself is the place to start. After all, it’s the one with the power to refund your money or issue credit, which can go a long way toward assuaging anger.

A disappointing response from an airline, however, can leave you feeling powerless. But Uncle Sam is on your side: since the mid ’80s, the Department of Transportation has held U.S.-based airlines responsible for customer-service issues. The first step is to file a complaint with the DOT’s Aviation Consumer Protection Division.

The division categorizes complaints by type — from oversales and fare misinformation to rude customer service and false advertising — and an analyst investigates each one. Not surprisingly, most passenger issues involve flight problems like cancellations or delays. These aren’t always the airline’s fault, of course. And passengers understand: the DOT says that complaints stemming from these incidents usually have more to do with the airline’s handling of the situation.

Serious issues are sent to the airlines for a resolution, but all problems — no matter how large or small — are tallied in a monthly public report of complaints per 100,000 “enplanements” (one passenger boarding one flight). And that must cause the airlines some degree of embarrassment, right?

Still, while a push from the DOT may help your case, this forum doesn’t let you voice your anger to the world. To help with that, upset passengers can tweet, start a Facebook group, or register complaints on Web sites.

In fact, it was a bad airline experience that led Barcelona-based entrepreneur Andres Kello to start his own site: AirlineComplaints.org, which has almost 3,100 members. American Airlines receives the bulk of the site’s complaints, says Kello, but “complaints about Delta tend to be the most negative.”

So what airline is doing it right? On the DOT’s official report (on which we relied for our list), that would be Southwest — the perennial consumer favorite that registered the lowest number of complaints the past three years running. The airline’s fans continually remark on the friendly customer service, which Kello agrees can defuse a stressful trip. “Smiles,” he says, “don’t cost airlines a penny.”